The present invention relates to the use of solubilized, anionic polyurethanes in skin care compositions.
Polyurethanes are known in the art as thickeners for compositions containing surface-active agents and for their use in hair fixative applications. U.S. Pat. Nos. 5,626,840; 5,968,494; and 6,291,580 as well as European Patent Application 99102797.0 (Publication No. EP 0 937 541) all disclose polyurethanes with carboxylate functionality for hair fixative applications.
Polyurethanes are also known for other applications, including cosmetic compositions. However, such polyurethanes are typically formulated in the dispersed state. Polyurethane dispersions are easier to manufacture than solutions. However, dispersed polyurethanes may result in many undesirable properties when formulated in cosmetic formulations. Dispersed polyurethanes are not good film formers, and their use may result in greasy, harsh or uneven feel, long application times, shiny appearance, poor substantivity and/or grittiness.
Other polymers are commonly used in skin care formulas, such as polyacrylates and polymers prepared from alkenes. From a formulator's standpoint, those polymers suffer from the need to heat at elevated temperatures, optionally in the presence of neutralizing agents, to assist in solubilization.
Surprisingly, it has now been discovered that the use of anionic polyurethanes in a solubilized state contribute enhanced aesthetics to skin care compositions without the disadvantages of previously known compositions.